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[SOLVED] www.google.com CNAME www.l.google.com
Posted: Mon Aug 13, 2007 8:19 am
by Chris Corbyn
Code: Select all
;; ANSWER SECTION:
www.google.com. 331524 IN CNAME www.l.google.com.
www.l.google.com. 214 IN A 216.239.59.103
www.l.google.com. 214 IN A 216.239.59.104
www.l.google.com. 214 IN A 216.239.59.147
www.l.google.com. 214 IN A 216.239.59.99
Does anyone know if there's a practical reason why Google have CNAME'd
http://www.google.com to
http://www.l.google.com before they start the round robin? I only ask because I'm about to set up another cluster of servers which will round-robin but I can't see a reason to cname like this when it works if you just directly assign IPs to the actual domain. Unless maybe they use different domain names mapping to
http://www.l.google.com without the end-user thinking about it.
Posted: Sun Aug 19, 2007 4:37 pm
by Chris Corbyn
I think I realised why they've done this. I ended up coming to the same result myself. Basically if you have different domain names virtualhosted on the same hardware then you don't want to have to list all round-robin IP addresses multiple times for each domain name. It's far easier to have one domain name containing all the A records for the round-robin, then link each virtual hosted domain name to that round-robin by linking it by CNAME. Effectively it's a more maintainable way to offer redundancy

Posted: Sun Aug 19, 2007 4:59 pm
by Oren
I see... It's your monthly "self-discussion". Ok whatever, at least it took you just 2 posts this time. And as always, you solve the problem

Posted: Sun Aug 19, 2007 7:03 pm
by Chris Corbyn
My cries for help go unnoticed

then I discover the answer or have a braindump and feel the need to keep the thread updated

Posted: Sun Aug 19, 2007 10:27 pm
by Benjamin
I get a kick out it.
Posted: Mon Aug 20, 2007 12:42 am
by timvw
I forgot to post the answer

(A while ago i found some forum where a guy explained it.. Also notice that the TTL of the records between google.com and x.google.com)
Posted: Mon Aug 20, 2007 4:24 am
by Chris Corbyn
timvw wrote:Also notice that the TTL of the records between google.com and x.google.com)
Ah, I don't know why I didn't pick up on that. Good point, I should change our to do it that way. I just have all our TTL's set at 200 (even though a good chunk of DNS servers won't honour TTL properly

)
There's definitely no need to have a low TTL on the alias though
